A compound having a large absorption intensity in the range from 500 nm to 700 nm, especially a compound having a maximum absorption (λmax) in the range from 550 nm to 620 nm has been used as an optical element in an optical recording layer of optical recording media such as DVD-Rs, or in an optical filter for image display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), cathode ray tubes (CRTs), fluorescent display tubes, and field emission displays.
As the foregoing optical element, for example, in Patent Documents 1 and 2 described below, a cyanine compound containing a metallocene-bonded group has been reported. However, the optical element, which is used in an optical filter for image display devices and an optical recording material with laser light, is expected to have further improvement in such performances as lightfastness and solubility.
Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-171571
Patent Document 2: WO 2006/035555A